Hybrid CuTCNQ/AgTCNQ Metal‐Organic Charge Transfer Complexes via Galvanic Replacement vs Corrosion‐Recrystallization

This study reports a hybrid of two metal‐organic semiconductors that are based on organic charge transfer complexes of 7,7,8,8‐tetracyanoquinodimethane (TCNQ). It is shown that the spontaneous reaction between semiconducting microrods of CuTCNQ with Ag⁺ ions leads to the formation of a CuTCNQ/AgTCNQ hybrid, both in aqueous solution and acetonitrile, albeit with completely different reaction mechanisms. In an aqueous environment, the reaction proceeds by a complex galvanic replacement (GR) mechanism, wherein in addition to AgTCNQ nanowires, Ag⁰ nanoparticles and Cu(OH)₂ crystals decorate the surface of CuTCNQ microrods. Conversely, in acetonitrile, a GR mechanism is found to be thermodynamically unfavorable and instead a corrosion‐recrystallization mechanism leads to the decoration of CuTCNQ microrods with AgTCNQ nanoplates, resulting in a pure CuTCNQ/AgTCNQ hybrid metal‐organic charge transfer complex. While hybrids of two different inorganic semiconductors are regularly reported, this report pioneers the formation of a hybrid involving two metal‐organic semiconductors that will expand the scope of TCNQ‐based charge transfer complexes for improved catalysis, sensing, electronics, and biological applications.     

Evidence for cholesteric morphology in films of cellulose acetate butyrate by transmission electron microscopy

Summary Transmission electron microscopy provides direct evidence of helicoidal cholesteric morphology in films of cellulose acetate butyrate prepared by solvent casting from liquid crystalline solutions in dimethylacetamide. We believe this is the first observation reported of cholesteric structure in a mixed cellulosic ester. Cholesteric morphology was also observed in solvent cast blended films of cellulose acetate butyrate and lignin from liquid crystalline solutions. There are indications that lignin particles may be serving as nucleating surfaces or sites of direct termination for some of the observed cholesteric fingerprint pattern.     

Second-site cleavage in sterol regulatory element-binding protein occurs at transmembrane junction as determined by cysteine panning

In response to sterol deprivation, two sequential proteolytic cleavages release the NH2-terminal fragments of sterol regulatory element-binding proteins (SREBPs) from cell membranes. The fragments translocate to the nucleus where they activate genes involved in cholesterol and fatty acid metabolism. The SREBPs are bound to membranes in a hairpin fashion. The NH2-terminal and COOH-terminal domains face the cytoplasm, separated by two membrane spanning segments and a short lumenal loop. The first cleavage occurs at Site-1 in the lumenal loop. The NH2-terminal fragment is then released by cleavage at Site-2, which is believed to lie within the first transmembrane segment. Here, we use a novel cysteine panning method to identify the second cleavage site (Site-2) in human SREBP-2 as the Leu484-Cys485 bond that lies at the junction between the cytoplasmic NH2-terminal fragment and the first transmembrane segment. We transfected cells with cDNAs encoding fusion proteins with single cysteine residues at positions to the NH2-terminal and COOH-terminal sides of cysteine 485. The NH2-terminal fragments were tested for susceptibility to modification with Nalpha-(3-maleimidylpropionyl)biocytin, which attaches a biotin group to cysteine sulfhydryls. Cysteines to the NH2-terminal side of cysteine 485 were retained on the NH2-terminal fragment, but cysteines to the COOH-terminal side of leucine 484 were lost. Leucine 484 is three residues to the COOH-terminal side of the tetrapeptide Asp-Arg-Ser-Arg, which immediately precedes the first transmembrane segment and is required for Site-2 cleavage.     

A regular variational boundary model for free vibrations of magneto-electro-elastic structures

In this paper a regular variational boundary element formulation for dynamic analysis of two-dimensional magneto-electro-elastic domains is presented. The method is based on a hybrid variational principle expressed in terms of generalized magneto-electro-elastic variables. The domain variables are approximated by using a superposition of weighted regular fundamental solutions of the static magneto-electro-elastic problem, whereas the boundary variables are expressed in terms of nodal values. The variational principle coupled with the proposed discretization scheme leads to the calculation of frequency-independent and symmetric generalized stiffness and mass matrices. The generalized stiffness matrix is computed in terms of boundary integrals of regular kernels only. On the other hand, to achieve meaningful computational advantages, the domain integral defining the generalized mass matrix is reduced to the boundary through the use of the dual reciprocity method, although this implies the loss of symmetry. A purely boundary model is then obtained for the computation of the structural operators. The model can be directly used into standard assembly procedures for the analysis of non-homogeneous and layered structures. Additionally, the proposed approach presents some features that place it in the framework of the weak form meshless methods. Indeed, only a set of scattered points is actually needed for the variable interpolation, while a global background boundary mesh is only used for the integration of the influence coefficients. The results obtained show good agreement with those available in the literature proving the effectiveness of the proposed approach.     

Colorimetrische Bestimmung von Nitrat und Nitrit in biologischem Material

European Food Research and Technology - Die ausgearbeitete Methode zur Nitrat- und Nitritbestimmung beruht auf der colorimetrischen Bestimmung des durch Nitrierung entstehenden...     

Chemometric study of graft copolymerization of guar‐g‐(acrylamide‐co‐diallyl dimethylammonium chloride)

Chemometrics was employed to study the effect of various reaction conditions on the graft copolymerization of acrylamide (AM) and diallyl dimethylammonium chloride (DADMAC) onto guar gum using the cerous sulfate and potassium persulfate complex initiation system. A two level full factorial design was used to study the effect of reaction parameters on percentage grafting (%G) and monomer conversion (%MC). Synthesized polymers were characterized using Fourier transform infrared spectroscopy (FTIR), ¹H‐NMR (nuclear magnetic resonance spectroscopy), and ¹³C‐NMR and also were analyzed for differences in intrinsic viscosity and charge incurred with changing reaction conditions. The concentration of AM was observed to have the greater effect on %grafting. Interaction effects between the reaction temperature and concentration of AM were also found to be important. Under the reaction condition studied, the highest grafting (%G) was obtained for polymer 1 (0.7M AM concentration, 60°C reaction temperature, and 1M acid concentration). © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Interaction of malonaldehyde with collagen. III. Binding site characteristic of malonaldehyde with respect to collagen.

In this paper have been studied properties of a product that arose from the interaction of malonaldehyde with collagen. It has been shown by an amino acid analysis that malonaldehyde reacts in a significant way on lysine and tyrosine residues. The partcipation of tyrosine in the reaction with malonaldehyde has been further demonstrated by means of spectrophotometry. It has also been found that the hydrolysis by pronase is considerably modified with the cross linked collagen.     

Inadvertently high dialysate magnesium causing weakness and nausea in hemodialysis patients

As maintenance hemodialysis patients are exposed to large quantities of dialysis water, any contamination of it might be reflected in plasma levels. We present a series of cases due to such a contamination. Six maintenance hemodialysis patients dialyzing at the same peripheral hemodialysis facility presented to us over a short period of time with symptoms mimicking inadequate dialysis. Their blood urea and creatinine levels were not very high, but all the patients had hypermagnesemia [serum Mg levels = 1.8 (±0.3) mmol/L]. Except for one patient who had cardiac arrest at presentation, all patients improved after undergoing hemodialysis at our center [serum Mg at discharge = 0.86 (±0.01) mmol/L]. The origin of hypermagnesemia was traced to dialysis water contamination with magnesium due to inadequate maintenance of the water treatment system. Corrective measures improved the quality of water, and no further cases were reported from that center. Proper maintenance and periodic checks of the quality of water are central to the outcomes of maintenance hemodialysis patients.     

Discrete element method simulation of binary blend mixing of cohesive particles in a high-intensity vibration system

The effects of processing intensity, time, and particle surface energy on mixing of binary cohesive powder blends in high-intensity vibration system were investigated via discrete element method simulations. The mixedness was quantified by the coefficient of variation, C_v; lower being better. The mixing rate, which is the speed at which homogeneity was achieved, was inversely proportional to the mixing Bond number, defined as the ratio of particle cohesion to the shear force resulting from the mixing intensity. Results show that both increasing processing intensity and reducing surface energy led to a faster mixing rate. However, the mixedness improved initially as mixing action (the product of mixing rate and mixing time) increased, but later deteriorated upon its further increase. Thus, both mixing rate and mixing intensity need to be tuned for optimum mixing performance depending on the cohesion level of particles; too high or too low mixing action should be avoided.     

Possible Link between Higher Transmissibility of Alpha,Kappa and Delta Variants of SARS-CoV-2 and Increased Structural Stability of Its Spike Protein and hACE2 Affinity

The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) outbreak in December 2019 has caused a global pandemic. The rapid mutation rate in the virus has created alarming situations worldwide and is being attributed to the false negativity in RT-PCR tests. It has also increased the chances of reinfection and immune escape. Recently various lineages namely, B.1.1.7 (Alpha), B.1.617.1 (Kappa), B.1.617.2 (Delta) and B.1.617.3 have caused rapid infection around the globe. To understand the biophysical perspective, we have performed molecular dynamic simulations of four different spikes (receptor binding domain)-hACE2 complexes, namely wildtype (WT), Alpha variant (N501Y spike mutant), Kappa (L452R, E484Q) and Delta (L452R, T478K), and compared their dynamics, binding energy and molecular interactions. Our results show that mutation has caused significant increase in the binding energy between the spike and hACE2 in Alpha and Kappa variants. In the case of Kappa and Delta variants, the mutations at L452R, T478K and E484Q increased the stability and intra-chain interactions in the spike protein, which may change the interaction ability of neutralizing antibodies to these spike variants. Further, we found that the Alpha variant had increased hydrogen interaction with Lys353 of hACE2 and more binding affinity in comparison to WT. The current study provides the biophysical basis for understanding the molecular mechanism and rationale behind the increase in the transmissivity and infectivity of the mutants compared to wild-type SARS-CoV-2.